1. Field of the Invention
The present invention relates to an organic light-emitting display device and a method of driving the organic light-emitting display device. More particularly, the present invention relates to an active matrix organic light-emitting display device and a method of driving the organic light-emitting display device.
2. Description of the Related Art
Mobile communication needs have developed as life style changes have recently occurred, so that it is desirable that multimedia devices have a display device with lighter-weight, lower power consumption and slimmer shape than before. An organic light-emitting display device, which is one of the new display devices satisfying the above need, is a self-emitting type, so that display characteristics, such as a viewing angle, a contrast ratio and so on, are excellent compared to a liquid crystal display device. In addition, the organic light-emitting display device can be formed in a slim shape and consumes less power because a backlight is not required.
There are a passive matrix type and an active matrix type in the technology of organic light-emitting display devices. A positive electrode and a negative electrode are formed to cross each other and lines are selected for driving in the passive matrix type. On the other hand, in the active matrix, a driving voltage switched by a switching transistor is sustained with a capacitor and is applied to a driving transistor, so that an electric current in an organic light-emitting device is controlled.
However, characteristics of a threshold voltage of the driving transistor are different according to positions of the organic light-emitting display panel in a conventional organic light-emitting display device with the active matrix type. Such differences of the threshold voltage are caused by a process error in a manufacturing process of a thin film transistor (TFT). Even if an equivalent driving voltage is applied to the driving transistor of each of the pixels, the differences in the threshold voltage cause differences of electric current in the organic light-emitting device, so that each pixel displays different luminance as a consequence.
When a deviation of the threshold voltage of the driving transistor is generated in the organic light-emitting display panel, a defect in uniformity of luminance occurs, and spots display on the screen. The deviation of the threshold voltage of the driving transistor is different according to the organic light-emitting display panel, so that a black level and a white level are different according to the panel. Thus, panel characteristics such as brightness and contrast ratio are not constant for each of the organic light-emitting display panels.